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Rare Metals 2023年第3期42卷 1011-1017页

作者： fang-fang xu Yong Zhao Yue xu School of Chemistry and Environment Beihang UniversityBeijing 100191China

The poor corrosion resistance of magnesiumlithium alloy surface works against its application in aerospace,automobile,electronics,*** this research,some kinds of non-toxic and non-polluting rare earth and silane(RE-Si)composite conversion coatings were built up on Mg-Li alloy surface,and formation process of coatings was *** parameters for coating preparation were determined,including immersion time and temperature,pH value of conversion solution and curing *** optimized technological parameters for preparation of RE-Si composite coating were finally *** influence of doping nanoparticles on RE-Si composite coating was also discussed,and the microstructure of coatings shows that the addition of nanoparticles can effectively improve the compactness and uniformity of composite *** corrosion resistance of specimens with RE-Si composite conversion coating is improved to a great extent compared with those of substrate or specimens with single rare earth(RE)conversion coating or with silane *** result also indicates that corrosion resistance of RE-Si composite coating doping with nanoparticles is further *** of the composite coatings was analyzed,and the effect of RE elements and silane on coating formation process was *** resistance mechanism of composite coatings on Mg-Li alloy surface was discussed.

关键词： Magnesium-lithium alloy Rare earth-silane composite coating Nanoparticles Corrosion resistance

Superior compound coatings prepared by low-temperature vanadium-nitrocarburizing duplex treatment

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Rare Metals 2024年第4期43卷 1828-1835页

作者： Gen Jin fang-fang xu xun-xun Hu Yue xu School of Chemistry Beihang UniversityBeijing100191China Guobiao(Beijing)Testing and Certification Co. LtdBeijing100088China School of Materials Science and Engineering Beihang UniversityBeijing100191China

Superior compound coatings were prepared on CK45 steel surface by vanadium-nitrocarburizing duplex treatment in low-temperature salt *** this study,the microhardness,the phase constitution and the compositional distribution in the coatings prepared under different conditions were systematically *** results indicated that the reactions among activated vanadium,carbon and nitrogen atoms occurred on the steel surface,leading to the formation of compound coatings composed of outermost and compound *** mechanism for the formation of compound layer as well as the growth kinetics of the layer was also *** the duplex treatment,the wear and corrosion resistances of steel surface were significantly *** was found that the growth kinetics of compound layer obeyed the parabolic law,with the activation energy of 122.82 kJ·moL^(-1).

关键词： Vanadium-nitrocarburizing duplex treatment Compound coatings Microstructure Formation mechanism Growth kinetics

Randomized Algorithms for Orthogonal Nonnegative Matrix Factorization

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Journal of the Operations Research Society of China 2023年第2期11卷 327-345页

作者： Yong-Yong Chen fang-fang xu College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590ShandongChina

Orthogonal nonnegative matrix factorization(ONMF)is widely used in blind image separation problem,document classification,and human face *** model of ONMF can be efficiently solved by the alternating direction method of multipliers and hierarchical alternating least squares *** the given matrix is huge,the cost of computation and communication is too ***,ONMF becomes challenging in the large-scale *** random projection is an efficient method of dimensionality *** this paper,we apply the random projection to ONMF and propose two randomized *** experiments show that our proposed algorithms perform well on both simulated and real data.

关键词： Orthogonal nonnegative matrix factorization Random projection method Dimensionality reduction Augmented lagrangian method Hierarchical alternating least squares algorithm

Fast Implementation of Iterative Reconstruction with Exact Ray-Driven Projector on GPUs

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Tsinghua Science and Technology 2010年第1期15卷 30-35页

作者： fang xu Siemens Corporate Research Princeton NJ 08540 USA

Iterative methods are popular choices in image reconstruction fields due to their capability of recovering object information from incomplete acquisition data. However, the computation process involves frequent uses of forward and backward projections that are computationally expensive. Past research has proved that a forward projector that can produce high quality images is crucial to achieve a good convergence rate. In this paper a high performance iterative reconstruction framework is introduced, where two most popular iterative algorithms： Simultaneous Algebraic Reconstruction Technique （SART） and Ordered-subsets Expectation Maximization （OSEM） are supported. The framework utilizes Siddon＇s ray-driven method to generate forward projected images. Benefited from functionalities offered by current generation of graphics processing units （GPUs）, it achieves better performance when compared to previous GPU implementations that use grid-interpolated methods, on top of the significant speedups over CPU-based solutions.

关键词： image reconstruction tomography graphics processing units

糖尿病性白内障患者术后黄斑水肿的影响因素分析

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国际眼科杂志 2025年第1期25卷 140-143页

作者：李明徐方许之娟胶州中心医院眼科山东省青岛市266300

目的:探讨糖尿病性白内障患者手术治疗后发生黄斑水肿的危险因素,为术后防治提供参考依据。方法:选取青岛市胶州中心医院眼科2022-01/2024-01实施超声乳化手术治疗后且发生黄斑水肿的糖尿病性白内障患者55例55眼作为水肿组,另外年龄与... 详细信息

目的:探讨糖尿病性白内障患者手术治疗后发生黄斑水肿的危险因素,为术后防治提供参考依据。方法:选取青岛市胶州中心医院眼科2022-01/2024-01实施超声乳化手术治疗后且发生黄斑水肿的糖尿病性白内障患者55例55眼作为水肿组,另外年龄与性别基本匹配的接受相同手术治疗但未发生黄斑水肿的糖尿病性白内障患者59例59眼作为对照组,分析房水中干扰素诱导蛋白-10(IP-10)、巨噬细胞趋化蛋白-1(MCP-1)、血管内皮生长因子(VEGF)与患者术后黄斑水肿的关系。结果:水肿组的年龄、糖尿病病程、最佳矫正视力(BCVA)、糖化血红蛋白(HbA1c)、肌酐测定值、房水中IP-10、MCP-1、VEGF水平均大于对照组(均P<0.05);糖尿病病程延长、BCVA、HbA1c升高、肌酐升高及房水中IP-10升高、MCP-1升高、VEGF升高是糖尿病性白内障患者手术后发生黄斑水肿的危险因素(均P<0.05)。结论:糖尿病性白内障患者手术治疗后发生黄斑水肿与糖尿病病程延长、BCVA、HbA1c升高、肌酐升高及房水中IP-10升高、MCP-1升高、VEGF升高有关,临床应该针对性地提前给予干预措施。

关键词：糖尿病性白内障超声乳化手术白内障黄斑水肿危险因素

Q-Learning Based Interference-Aware Channel Handoff for Partially Observable Cognitive Radio Ad Hoc Networks

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Chinese Journal of Electronics 2017年第4期26卷 856-863页

作者： xu Ning ZHANG Huyin xu fang WANG Zhiyong Department of Computer Wuhan University

Channel handoff is a crucial function for Cognitive radio ad hoc networks(CRAHNs). The absence of centralized infrastructures and the limited power make the handoff design more challenging. A learningbased interference-aware handoff scheme is proposed for distributed CRAHNs. We model the channel handoff process as a Partially observable Markov decision process(POMDP) and adopt a Q-learning algorithm to find an optimal handoff strategy in a long term. The proposed algorithm obtains an efficient transmission performance by considering the interferences among SUs and PUs. To achieve PU awareness, the handoff scheme predicts the PU activities by using the historical channel usage statistics. In addition, we also propose a refined channel selection rule to compromise between learning speed and cumulative transmission reward. The simulation results show that the proposed handoff scheme can adapt to the PU activities and achieves a better performance in terms of high throughput and low collisions. And the learning process keeps a considerable balance between convergence time and cumulative reward.

关键词： Cognitive radio Ad hoc networks Partially observable Markov decision process(POMDP) Handoff Q-Learning

Gamma-Dirichlet algebra and applications

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Frontiers of Mathematics in China 2014年第4期9卷 797-812页

作者： Shui FENG fang xu Department of Mathematics and Statistics McMaster University Hamilton Ont L8S 4K1 Canada Canadian Imperial Bank of Commerce 21 Melinda St Toronto Ont M5L 1B9 Canada

The Gamma-Dirichlet algebra corresponds to the decomposition of the gamma process into the independent product of a gamma random variable and a Dirichlet process. This structure allows us to study the properties of the Dirichlet process through the gamma process and vice versa. In this article, we begin with a brief survey of several existing results concerning this structure. New results are then obtained for the large deviations of the jump sizes of the gamma process and the quasi-invariance of the two-parameter Poisson-Dirichlet distribution. We finish the paper with the derivation of the transition function of the Fleming-Viot process with parent independent mutation from the transition function of the measure-valued branching diffusion with immigration by exploring the Gamma-Dirichlet algebra embedded in these processes. This last result is motivated by an open R. C. Gritfiths. problem proposed by S. N. Ethier and

关键词： Coalescent Dirichlet process gamma process quasi-invariant,random time-change

A Double Varying-coefficient Modeling Approach for Analyzing Longitudinal Observations

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Acta Mathematicae Applicatae Sinica 2019年第3期35卷 671-688页

作者： Qun-fang xu Rui LI School of Business Ningbo UniversityNingbo 315211China School of Statistics and Information Shanghai University of International Business and EconomicsShanghai 201620China Key Laboratory of Advanced Theory and Application in Statistics and Data Science East China Normal UniversityMinistry of EducationShanghai 200062China

The identification of within-subject dependence is important for constructing efficient estimation in longitudinal data *** this paper,we proposed a flexible way to study this dependence by using nonparametric regression ***,we considered the estimation of varying coefficient longitudinal data model with non-stationary varying coefficient autoregressive error process over observational time *** on spline approximation and local polynomial techniques,we proposed a two-stage nonparametric estimation for unknown functional coefficients and didn’t not drop any observations in a hybrid least square loss ***,we showed that the estimated coefficient functions are asymptotically normal and derived the asymptotic biases and variances *** Carlo studies and two real applications were conducted for illustrating the performance of our proposed methods.

关键词： autoregressive process double varying coefficient irregular time quantum locally linear

Efcient Estimation of Varying Coefcient Seemly Unrelated Regression Model

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Acta Mathematicae Applicatae Sinica 2014年第1期30卷 119-144页

作者： Qun-fang xu Yang BAI School of Sciences Zhejiang Agriculture and Forestry University School of Statistics and Management Shanghai University of Finance and Economics Key Laboratory of Mathematical Economics (SUFE) Ministry of Education

In this paper, we propose a class of varying coefficient seemingly unrelated regression models, in which the errors are correlated across the equations. By applying the series approximation and taking the contemporaneous correlations into account, we propose an efficient generalized least squares series estimation for the unknown coefficient functions. The consistency and asymptotic normality of the resulting estimators are established. In comparison with the ordinary/east squares ones, the proposed estimators are more efficient with smaller asymptotical variances. Some simulgtlon＇studies and a real application are presented to demonstrate the finite sample performance of the proposed methods. In addition, based on a B-spline approximation, we deduce the asymptotic bias and variance of the proposed estimators.

关键词： series approximation varying coefficient seemingly unrelated regression contemporaneous correlation asymptotic normality

AMC-based resource allocation in adaptive frequency reused OFDMA-relay networks

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The Journal of China Universities of Posts and Telecommunications 2011年第2期18卷 59-64,71页

作者： CHEN Yu fang xu-ming School of Information Science and Technology Southwest Jiaotong University Chengdu 610031 China

In orthogonal frequency division multiple access（OFDMA） relay system,for supporting relay transmission,the base station（BS）-the relay station（RS） link must consume an extra part of resource,which may result in serious resource *** order to improve resource utilization,this paper proposes a dynamic resource allocation scheme in adaptive frequency reused OFDMA-relay system based on adaptive modulation and coding（AMC） *** this scheme,relay nodes have two independent antennas and operate in decode-and-forward（DF） and full-duplex *** the BS and RSs share the same subcarriers by spatial multiplexing by two independent *** resource allocation problem is formulated for system downlink throughput *** the optimal solution couldn＇t be obtained easily,a sub-optimal algorithm is *** adaptive frequency reused algorithm with two independent antennas RS improves the system throughput about 24.3 % compared with the orthogonal frequency allocation with single-antenna model,and increases the system throughput 10.4 % compared with adaptive frequency reused algorithms with single-antenna *** is proved that both of the RS with two-antenna model and adaptive frequency reused scheme can improve the system throughput significantly.

关键词： AMC resource allocation adaptive frequency reuse OFDMA relay